To find some water, let us look at the sky
By Denis Delbecq • June 16th, 2008 in 10:58 · Category: Actuality
Since GPS is free, so much to use it. It is the currency of an American team that tries to show that signals issued by the American satellites of positioning allow to follow with hindsight the humidity of soil in the arid regions. They publish their jobs in GPS Solutions, a magazine specialised in the "misappropriations" of the American system of positioning.
The signal picked up by a receiver GPS is complex: he blends the waves which reach directly of the satellite and those who were reflected by obstacles, starting with the soil. The microwaves of the system GPS are better reflected by the humid soil than the surfaces dried out. The team driven by Kristine Larsson and Eric Small (University of the Colorado) found a way to measure directly the wave reflected by the soil. The device was tested during seventy days with the aid of a fixed receiver GPS installed in Ouzbékistan, in Tashkent. The researchers determined a consecutive increase of thoughtful waves in every torrential rain, with a regular reduction during ten days which follow.
In the panoply of the sniffers of water, satellites capable of measuring the humidity of soil have a big disadvantage. Their space precision is a little "vague “, in the order of 40 - 60 km, estimate Larsson and his colleagues. The analysis of the signals of GPS would allow her better one selectivity of zones favourable to cultures, with a delicacy of some dozens metres.
It is not the first time when scientists divert the flux of waves of GPS in their benefit. The European Space Agency had united a symposium last October to prepare programmes of applications scientist of the future European system of positioning by satellite Galileo.
Picture: the future system of European positioning Galileo © ESA
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